In recent years, in an increasing number of variety of electronic equipment, particularly portable terminal equipment such as a cellular phone, in order to facilitate pressing of buttons and identification as well as operation of a display sheet and the like even in dark surroundings, a light emitting diode, an EL device or the like is made to emit light for illumination of an operational section. Also as a movable contact body and a switch for use in the equipment, ones easy to use and capable of making diverse illumination have been desired.
Such a conventional light guiding sheet and a movable contact body are described with reference to FIG. 3. It is to be noted that this drawing is represented by partially enlarging its size for the sake of facilitating understanding of its configuration.
FIG. 3 is a sectional view of a conventional switch. In FIG. 3, there is shown transmissive film-shaped base material 1. On the under surface of this base material 1, a plurality of light emitting sections 2 formed in a concavo-convex shape are provided, to form light guiding sheet 3.
There are also shown film-shaped base sheet 4 and substantially dome-shaped movable contact 5 made of a conductive metal sheet. A predetermined area of the outer periphery of base sheet 4 is attached to the under surface of light guiding sheet 3 with an adhesive (not shown), and the plurality of movable contacts 5 are attached to the under surface of base sheet 4 below light emitting sections 2, to constitute movable contact body 6.
Wiring substrate 7 has a plurality of wiring patterns (not shown) formed on its top and under surfaces. Provided on the top surface of wiring substrate 7 are a plurality of fixed contacts 8 each formed of central fixed contact 8A in a substantially circular shape and outer fixed contact 8B in a substantially horse hoof shape or a substantially ring shape to surround central fixed contact 8A.
Movable contact body 6 is attached to the top surface of wiring substrate 7. The outer periphery of each of movable contacts 5 in movable contact body 6 is placed on outer fixed contact 8B, and the center of the under surface of movable contact 5 is opposed to central fixed contact 8A with a predetermined spacing.
There are mounted a plurality of light emitting elements 9, such as light emitting diodes, on the top surface of wiring substrate 7 on a side of light guiding sheet 3 so as to be arranged, for example, with light emitting surfaces thereof being oriented toward the right end surface of base material 1.
Transmissive film-shaped display sheet 10 has light shielding section 10A formed on the under surface of the display sheet by printing or the like, and predetermined areas of light shielding section 10A are cut out in the shapes of a letter, a symbol or the like to form a plurality of display sections 10B. Display sections 10B are arranged above the plurality of light emitting sections 2 of light guiding sheet 3, to constitute a switch.
The switch as thus configured is mounted on an operational surface of electronic equipment, and the plurality of central fixed contacts 8A, outer fixed contacts 8B as well as the plurality of light emitting devices 9 are connected to an electronic circuit (not shown) of the equipment through the wiring patterns or the like.
In the above configuration, when a downward pressing operation is performed on predetermined display section 10B of display sheet 10, light guiding sheet 3 and base sheet 4 are bent to press the substantially dome-shaped central section of movable contact 5. When predetermined pressing force is applied, movable contact 5 is elastically reversed downward with a click feeling. By the center of the under surface of movable contact 5 coming into contact with central fixed contact 8A, central fixed contact 8A and outer fixed contact 8B come into the state of being electrically connected with each other though movable contact 5.
Further, when the pressing force applied to display sheet 10 is released, movable contact 5 is elastically reversed upward by elastic returning force. The center of the under surface of movable contact 5 leaves central fixed contact 8A, and central fixed contact 8A and outer fixed contact 8B come into the state of being electrically disconnected from each other.
In accordance with electrical connection and disconnection at fixed contact 8, switching of each function is performed in the equipment. Further, when power is supplied from the electronic circuit of the equipment to the plurality of light emitting devices 9, light emitting devices 9 emit light, and such light is introduced into light guiding sheet 3 from the right end surface and propagates left inside base material 1 while being reflected therein.
This light is diffused and reflected on the plurality of light emitting sections 2 on the under surface of base material 1, to illuminate from below display section 10B of display sheet 10. By illumination of the plurality of display sections 10B, display of a letter, a symbol and the like on display section 10B can be identified, so as to facilitate operation.
Consequently, the conventional switch is configured as follows. A pressing operation is performed on display sheet 10 to press the top surface of light guiding sheet 3 and make movable contact 5 elastically reversed, so as to electrically connect and disconnect at fixed contact 8. Further, light of light emitting devices 9 is introduced into light guiding sheet 3 from the end surface, to cause the plurality of light emitting sections 2 to emit light, so as to illuminate the plurality of display sections 10B of display sheet 10.
It is to be noted that, as related art document information relevant to the invention of this application, there is known, for example, Japanese Patent Unexamined Publication No. 2007-87749.
In above-mentioned conventional light guiding sheet 3 and movable contact body 6, a material for the plurality of light emitting sections 2 formed in a concavo-convex shape is the same as that for base material 1, and a light refractive index thereof is also the same as that of base material 1. It is difficult to cause the plurality of light emitting sections 2 to keep emitting light of sufficient brightness with a small number of light emitting devices 9. It is thus necessary to arrange a large number of light emitting devices 9 on the outer periphery of light guiding sheet 3 for bright and uniform illumination. This causes light guiding sheet 3 and movable contact body 6 to have complex configurations and to be expensive.